Heat treat furnace

ABSTRACT

A heat treat furnace having at least one radiator channel along a wall having heat radiators therein with a blower exhausting air into the channel horizontally at one end of the channel and with the channel exhausting air horizontally into the furnace interior at the other end of the channel. The blower suction side draws air horizontally from the furnace interior so that heated air is recirculated in the furnace interior horizontally to effect homogeneous heating of metal items in the furnace from top to bottom, side to side and end to end by air recirculation in horizontal travel to oppose and reduce gravitational and density influences toward stratification.

Jan. 2, 1973 United States Patent [191 Leland Primary Examiner-John J. Camby Attorney-Dale A. Winnie Claude H. Leland, Grosse Pointe, Mich.

[73] Assignee: Super Steel Treating Co., Warren,

[54] HEAT TREAT FURNACE [75] Inventor:

ABSTRACT A heat treat furnace having at least one radiator chan- Mich.

Mal'ch 1971 nel along a wall having heat radiators therein with a [211 App. N03 129,338 blower exhausting air into the channel horizontally at onev end of the channel and with the channel exhausting air horizontally into the furnace interior at the [22] Filed:

RELATED U.S. APPLICATION DATA Continuation-in-part of Ser.

other end of the channel. The blower suction side draws air horizontally from the furnace interior so that Aug. 22, 1969, Pat. No. 3,584,852

heated air is recirculated in the furnace interior horizontally to effect homogeneous heating of metal [58] Field of Search R 41 42 R 43 42 and end to end by air recirculation in horizontal travel to oppose and reduce gravitational and density influences toward stratification.

15 Claims, 7 Drawing Figures [56] References Cited UNITED STATES PATENTS 3,584,852 6/1971 Leland.................,............. 3,620,515 11/1971 Usiaketal.........................

PATENTEDJM 21m 3,708,156

ATTO RNEYS PATENTEDJAN 2m 3.708.156

SHEET 4 UF 4 INVENTOR.

AI 10mm 3 HEAT TREAT FURNACE This application is a continuation-in-part of copending Ser. No. 852,393 now U. S. Pat. No. 3,584,852.

BACKGROUND OF THE INVENTION Heretofore various designs of heat treat furnaces have been proposed. All of such prior art furnaces had one common characteristic, that is, having the heated air flow directed therethrough in a generally vertical flow pattern. Some had the heated air blown from a higher level to a lower level while others had the air flow in reverse thereto.

Such prior art furnaces are subject to temperature stratification arising from gravitational and density variations in the heated air. Further, many of such prior art furnaces required the digging of pits within the factory or facility housing the furnace while others were of extremely long overall length.

Generally, such prior art heat treat furnaces have not proven entirely satisfactory in that they are generally complicated in design and construction, expensive to manufacture, of less than desirable efficiency and do not treat the metal items with desirable uniformity.

Accordingly, the invention as herein disclosed and described is primarily directed to the solution of the above as well as other related problems.

SUMMARY OF THE INVENTION According to the invention, a heat treat furnace comprises a floor assembly for supporting metal items to be heat treated, first and second side walls, a ceiling wall, first and second end walls, a door in said first end .wall for enabling the placing and removing of said metal items from the interior of said furnace, a first baffie wall lying generally parallel to and relatively closely spaced from said first side wall, said first baffle wall leading from said second end wall and terminating short of said first end wall, said first baffle wall and said first side wall creating a first radiator channel having an open end spaced from said first end wall, first heat radiator means between said first baffle wall and said first side wall in said first radiator channel, blower means having a suction side and an exhaust side at said second end wall, first and second air return port means in said second end wall leading from said interior of said furnace to said suction side, a first air delivery port in said second end wall leading from said exhaust side to said first radiator channel, a second baffle wall lying generally parallel to and relatively closely spaced from said second side wall, said second baffle wall leading from said second end wall and terminating short of said first end wall, said second baffle wall and said second side wall creating a second radiator channel having an open end spaced from said first end wall, second heat radiator means between said second baffle wall and said second sidewall in said second radiator channel, a second air delivery port in said second end wall leading from said exhaust side to said second radiator channel, and third heat radiator means situated in relatively close proximity to said second end wall and generally between said first and second air return port means, said blower means thereby drawing air horizontally from the interior of said furnace and delivering the air horizontally to said first and second radiator channels to pass the air horizontally over said first and second heat radiator means to heat the air, said first and second radiator channels emitting the heated air horizontally to the interior of said furnace adjacent said first end wall at points remote from said air return port means in said second end wall, the heated air in moving from said radiator channels to said air return port means under influence of said blower means being effective to pass horizontally over the said metal items to impart heat thereto.

Various general and specific objects and advantages of the invention will become apparent when reference is made to the following detailed description of the invention considered in conjunction with the accompanying drawings.

Description of the Drawings In the drawings where, for purposes of clarity, certain details and elements may be omitted from one or more views:

FIG. 1 is a front elevational view of a furnace embodying the invention;

FIG. 2 is a side elevational view taken generally on the plane of line 22 in FIG. 1 and looking in the directly of the arrows;

FIG. 3 is an enlarged cross-sectional view taken generally on the plane of line 3-3 of FIG. 1 and looking in the direction of the arrows;

FIG. 4 is a vertical cross-sectional view taken generally on the plane of line 4-4 of either FIG. 1 or FIG. 3 and looking in the direction of the arrows;

FIG. 5 is a fragmentary vertical cross-sectional view taken generally on the plane of line 5-5 of FIG. 3 and looking in the direction of the arrows;

FIG. 6 is a view generally similar to FIG. 3 but illustrated in somewhat simplified or schematic form; and

FIG. 7 is an enlarged fragmentary cross-sectional view taken generally on the plane of line 77 of FIG. 6 and looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in greater detail to the drawings, FIG. 1 illustrates in front elevational view a heat treat furnace 10 constructed in accordance with the invention as comprising left and right side walls 12 and 14, outer supports or framing members 16 and left and right vertically extending guide rails 18 and 20 slideably containing therebetween a door 22 which, as shown, is in its closed position.

.As shown in FIG. 2, the furnace 10 also includes a base 24 situated atop, for example, a floor 26 of a related building structure. Further, as also shown in FIG. 2 suitable conduitry 28 and related pressure regulating valves and metering valves are provided for supplying a desired rate of fuel flow, suchas a combustible gas, from a related source (not shown) to the manifold 30 leading to the individual burner tubes. The forward wall 32 is situated immediately rearwardly of the door 22 (not shown in FIG. 2) while the rear wall 34 also serves to support associated air duct means and electric motor powered blower assemblies .36.

As generally illustrated in FIGS. 2, 3, 4 and 5 a plurality of banks of burner or radiator tubes are provided so as to be respectively situated inwardly of the op-' situated as to be h other and As Shown gen spaced inward e 50 of the left wall assembl Sinr I a ill km; my mum.

tion, the upper edges 136 of the curtain 118 and 120 are brought into close proximity to the inner surface 138 of the insulation 82, as generally depicted in FIG. 7. The nut 128 and threaded portion 126 may, of course, be employed for purposes of vertical adjustment.

As shown in each of FIGS. 3, 4 and 5, each curtain or wall 118 and 120 is formed to have a generally convoluted configuration with the convolutions extending generally vertically. While the upper ends of the curtains 118 and 120 are retained by hangers 122, the lower ends of both curtains are hanging freely except for straddling tupe of abutment assemblies 140, 142, 144 and 146 along the lower edge of curtain 118 and abutment assemblies 148, 150, 152 and 154 along the lower edge of curtain 120. Typically, each of the abutment assemblies is comprised of upwardly extending opposed abutment arms 156 and 158 which are so spaced as to accept therebetween the lower end of the respective curtain 118 or 120.

As generally depicted in FIGS. 4 and 5, each of the abutment arms 156 and 158 of each of the abutment assemblies extends downwardly as to be supported by and suitably connected, as by welding, to the lower outer metal wall 93 of the floor assembly 92. For this purpose, the lower ends of abutment arms 156 and 158 may, if desired, be suitably flanged or even connected to each other as to form a general U-shaped configuration. The purpose of such abutment assemblies is to confine any lateral movement of the curtains 118 and 120 while, at the same time permitting the lower edges 160 of each of the curtains to move towards and away from the layer of insulation 84 as the curtains expand and contract due to heating and cooling thereof. In view of the preceding it should be observed that wall or curtain 118 in combination with the left side wall assembly 12 define a first channel or passageway 162 therebetween while wall or curtain 120 in combination with the right side wall assembly 14 define a second channel or passageway 164.

As shown in both FIGS. 2 and 3, motor driven blower or fan means 36 are situated externally of the furnace housing and generally secured to the rear wall assembly 34. The right blower assembly 36a is comprised of a V rotatable blower or fan 168a which is operatively connected to a shaft 170a in turn driven by a belt 172a connected to a related motor 174a. The housing 166a has connected thereto intake ducting or passagemeans 176a, which is in communication with an inlet aperture 178a formed in the rear wall assembly 34, and outlet or supply ducting passage means 180a which is in commu nication with an aperture 182a formed in the reas wall assembly 34 as to be in communication with the passageway or channel 164. Like reference numerals in FIG. 3 suffiexed with b correspond to elements having like reference numbers with a suffix a. It should be mentioned that in one successful embodiment of the invention the capacity of each blower assembly was 15,000.00 cubic fee/minute. Therefore, the total rate of air flow through the furnace assembly was in the order of 30,000.00 cubic feet/minute.

In the preferred embodiment of the invention extra burner means in the form of an additional burner tube 184 is provided as to be situated generally in relatively close proximity to the rear wall assembly 34. The burner or radiator tube 184 is fed with fuel in the same manner as the other burner tubes (previously described) and is constructed as to be as the others typically disclosed to comprise a bight portion 64, leg portions 66, 68 and upper exposed ends 70 and 72.

OPERATION OF INVENTION The operation of the invention is generally as follows. After the door 22 is elevated in the guide tracks 18 and 20, the metal items to be heat treated are loaded within the interior chamber 200 of the furnace l0 and situated atop the supports 94, 96, 98, 100, 102 and 104. For purposes of illustration members 202, 204, 206 and 208 are illustrated in phantom line in FIG. 3; such members may, for purpose of discussion, comprise vertically extending stacks of coiled metal rod to be heat treated.

It should be noted that the spaced location of supports or platforms 94, 96, 98 and 100, 102, 104 provide an added benefit. That is, because of the relatively great weight of articles to be heat treated, mechanical means must be employed in the loading and unloading process. Accordingly, the longitudinal spaces between platforms 94 and 96, 96 and 98, 100 and 102, and 102 and 104 provide enough space for the tangs of a fork lift truck to pass therethrough in order to enable the articles 202, 204, 206 and 208 to be sequentially introduced into chamber 200 and set down atop the platforms 94, 96, 98, 100, 102 and 104 in positions as shown. After the articles to be heat treated are so placed, the fork lift truck tangs can be withdrawn through such spaced between the plat form.

Once the furnace 10 is loaded and door 22 is closed, fuel is fed to burner tubes 40, 42, 44, 46, 48, 52, 54,56, 58, 60 and 184 in order to start providing heat to the chamber 200 and blower assemblies 36a and 36b are actuated to start the flow of air through the interior of the furnace 10.

The air flow within the furnace 10 is presented in a horizontal pattern. That is, for example, the blower 168a supplies air through conduit means 180a, through port 182a and into the channel or passageway 164 where, because of the curtain being substantially closed at the top and bottom, the air flows through the channel 164 until it approaches the front wall of the furnace 10 where it then turns generally inwardly and flows over, through and about the articles 206, 208 on its way back to the blower inlet 178a and 176a. Similarly, blower 16812 supplies air through conduit means 18012, through port 182b and into the channel or passageway 162 where, because of the curtain 118 being substantially closed at the top and bottom, the air flows through the channel 162 until it approaches the front wall of the furnace 10 where it then turns generally inwardly and flows over, through and about the articles 202 and 204 on its way back to the blower inlet l78b and 176b.

It has been discovered that such horizontal flow of air efi'ectively overcomes the tendency of heat stratification, due to density changes, of the air, as experienced by the prior art vertical air flow furnaces.

FIG. 6 is a view generally similar to FIG. 3 but illustrated in a somewhat schematic or simplified manner. The main purpose of FIG. 6 is to generally pictorially illustrate the heat and air flows within the furnace chamber 200 during operation. From FIG. 6 it will be observed that the walls 118 and 120 not only serve to define passages 162 and 164 but also combine with the burner tubes to form heat radiating means whereby radiant heat is directed, as generally depicted by the wavey arrows 210 toward the pieces being heat treated. Although any suitable configurations of curtains 118 and 120 may be employed, it is, nevertheless, preferred that such curtains have an uneven surface thereby adding to the overall effective surface area for heat transfer from the associated burner tubes and, at the same time, tend to enhance the establishment of eddy currents in the air flow as to make the temperature of such air flow of even greater uniformity. Accordingly, the preferred embodiment of the invention employs curtains 1 18 and 120 of a convoluted configuration.

Now, condiering only one air delivery system, for example, blower assembly 36a, it can be seen that the air flow generated thereby is depicted by the broad arrows and that the coldest air would be that entering the inlet 182a of channel 164. As the air passes through channel 164 and about the burner tubes situated therein, the temperature of the air increases until it reaches a maximum temperature in the general zone of last burner tube 60. As the air moves generally about the work to be heat treated it continues to move toward the blower inlet 178a and during such movement continues to decrease in temperature from the point of maximum temperature as at burner 60, to the blower inlet 178a.

It has been determined that because of such heat loss of the air, the articles being heat treated and closest to the blower inlet 1780 have a tendency to at times to be exposed to insufficient heat in the sector depicted generally by the phantom line 212. Therefore, in order to assure sufficient heat for section 212, as well as sector 214 on the opposite side, the additional burner tube 184 is provided as shown thereby enabling radiant heat, as depicted by wavy arrows 216, to be directed to such sectors.

Generally, it can be seen that if, for example, twothirds of the available heat energy on the right side is transmitted by the radiating means comprised of curtain 120 and burner tubes 52, 54, 56, 58 and 60 then one-third of the available heat energy is transmitted by the air flow passing generally through the middle of the chamber 200. However, under this assumption, twothirds of the available heat energy on the left side would be transmitted by the radiating means comprised of curtain 118 and burner tubes 40, 42, 44, and 48; therefore, one third of that available heat energy would be transmitted by the air flow passing therefrom and generally through the middle of the chamber 200. In view of the above, it can be seen that virtually all portions of the articles under heat treat are exposed to substantially the same heat energy regardless of its position within the furnace or the height of such articles.

As generally depicted in FIGS. 3, 4, and 6, the preferred embodiment of the invention employs a plurality of thermocouple type heat sensors 218, 220, 222 A and 224. As generally shown by 220 in FIG. 4, each of the temperature sensors is situated as to extend through its associated wall assembly and connected related control means which, as is well known in the art, in turn functions to control the rate of fuel flow to the various burner tubes.

Although only one preferred embodiment of the invention has been disclosed and described it is apparent that other embodiment and modifications of the invention are possible within the scope of the appended claims.

I claim:

1. A heat treat furnace, comprising a floor, a ceiling wall, a first side wall, a second side wall, a front wall, a rear wall, first heat generating and radiating means situated within the interior of said furnace and in relatively close proximity to said first side wall so as to define a first air passage extending from and having a first inlet near said rear wall toward said front wall, said first air passage including an outlet nearer said front wall, second heat generating and radiating means situated within the interior of said furnace and in relatively close proximity to said second side wall so as to define a second air passage extending from and having a second inlet near said rear wall toward said front wall, said second air passage including an outlet nearer said front wall, third passage means formed through a wall of said furnace in communication with said first inlet, fourth passage means formed through a wall of said furnace in communication with said second inlet, fifth passage means formed through said rear wall, said third fourth and fifth passage means being adapted for connection to associated air blower means whereby said third and fourth passage means are effective for directing air supplied by the discharge side of said blower means to said first and second air passages respectively, and whereby said fifth passage means is effective to accept and direct the air flowing horizontally from said first and second outlets and subsequently passing toward the rear wall to the inlet side of said associated blower means, and additional heat generating and radiating means situated in relatively close proximity to said rear wall inwardly thereof, said additional heat generating and radiating means being situated generally between said first and second side walls.

2. A heat treat furnace according to claim 1, wherein said first heat generating and radiating means comprises a generally vertically extending baffle wall spaced from said first side wall and generally parallel thereto, a plurality of heat generating sources situated generally between said baffle wall and said first side wall, and wherein said baffle wall is formed'to have an irregular vertically extending surface.

3. A heat treat furnace according to claim 1, wherein said first heat generating and radiating means comprises a generally vertically extending baffle wall spaced from said first side wall and generally parallel thereto, a first pluraiity of heat generating sources situated generally between said baffle wall and said first side wall, and wherein said baffle wall is of a convoluted configuration with the convolutions thereof extending generally vertically.

4. A heat treat furnace according to claim 2, wherein said baffle wall has a top edge in close proximity to the ceiling of the interior of said furnace and generally fixedly retained in said close proximity, and wherein said baffle wall has a bottom edge constrained against laterial movement but free to raise and lower in accordance with contraction and expansion thereof due to temperature changes in said baffle wall.

5. A heat treat furnace according to claim 4, including abutment means carried by said floor for constraining said lateral movement of said baffle wall, said abutment means comprising first and second abutment portions situated near said bottom ends and disposed on opposite sides of said baffle wall.

6. A heat treat furnace according to claim 4, including baffle wall supporting means, said baffle wall supporting means comprising a plurality of hanger assemblies for supporting said baffle wall from said ceiling wall, each of said hanger assemblies comprising a main body portion extending upwardly through said ceiling wall as to have an upper end projecting beyond the top of said ceiling wall, a lower hook-like portion carried by said main body portion for reception through an accommodating aperture formed in said baffle wall near the upper edge thereof, and adjustment means cooperating with said upper projecting end for varying the heights of said hook-like portion relative to said ceiling wall.

7. A heat treat furnace according to claim 1, wherein said first heat generating and radiating means comprises a generally vertically extending first baffle wall spaced from said first side wall and generally parallel thereto, a first plurality of heat generating sources situated generally between said first baffle wall and said first side wall, wherein said second heat generating and radiating means comprises a generally vertically extending second baffle wall spaced from said second side wall and generally parallel thereto, a second plurality of heat generating sources situated generally between said second baffle wall and said second side wall, and wherein each of said baffle walls has its top and bottom edges in at least close proximity respectively to said ceiling wall and a floor of the interior of said furnace.

8. A heat treat furnace according to claim 7, wherein each of said baffle walls is hangingly supported from said ceiling wall, and wherein each of said baffle walls terminates short of said front wall in order to thereby define said first and second outlets as having a height substantially equal to the vertical distance from said floor to said ceiling.

9. A heat treat furnace according to claim 7, wherein said first and second plurality of heat generating sources each comprise a plurality of generally U- shaped burner tubes extending vertically between respective ones of said baffle walls and related side walls.

10. A heat treat furnace according to claim 7, wherein said floor comprises a lower outer metal wall, a plurality of platform like support surfaces extending generally from said front wall toward said rear wall, a first layer of mineral fiber insulation placed adjacent the inner surface of said lower outer metal wall, and a second layer of insulation placed adjacent the innermost surface of said first layer of insulation, said second layer of insulation being of blanket-like configuration and composed or constituents high in percentages of alumina and silicon oxide.

11. A heat treat furnace according to claim 7, wherein each of said side, rear, front and ceiling walls is comprised of an outer metal wall, a first layer of insulating material placed adjacent the inward surface of said outer metal wall, a second layer of insulating material placed adjacent the inward surface of said first means for holding said layers of insulating material in position, said retaining means comprising a plurality of spaced hanger-like rods arranged as to be generally normal to and secured at respective one ends to said outer metal wall, said layers of insulating material being generally skewered onto said hanger-like rods and retained thereon by suitable removeable abutments carried generally near the respective other ends of said hanger-like rods 12. A heat treat furnace according to claim 11, wherein said first layer of insulating material comprises block form 'mineral fiber insulation;

13. A heat treat furnace according to claim 1, wherein said fifth passage means comprises horizontally spaced first and second outlet conduit means, and wherein additional heat generating and radiating means I is situated generally between said first and second outlayer of insulating material, and including retaining let conduit means.

14. A heat treat furnace according to claim 13, wherein said additional heat generating and radiating means comprises a generally vertically extending U shaped burner tube.

15. A furnace for heat treating such as annealing, normalizing, and stress-relieving metal items; said furnace having a structure and operation comprising a floor for supporting metal items to be treated, first and second side walls, first and second end walls rising from said floor, a ceiling wall on said side walls and end walls, and a door in one said wall for placing and removing metal items in said furnace, a baffle wall lying parallel to and relatively closely spaced from said first side wall, said baffle wall leading; from said first end wall and terminating short of said second end wall, said baffle wall and said first side wall creating a radiator channel having an open end spaced from said second end wall, heat radiators between said first side wall and said baffle wall in said radiator channel, a blower having a suction side and an exhaust side at said first end wall, an air return port in said first end wall leading from the furnace interior to said blower suction side, an air delivery port in said first end wall leading from said blower exhaust side to said radiator channel between said baffle wall and said first side wall, and additional heat radiator means situated in relatively close proximity to said first end wall and said air return port, said blower thereby drawing air horizontally from the interior of said furnace walls and delivering the air horizontally to said radiator channel to pass the air horizontally over said radiators in said channel to heat the air, said radiator channel emitting the heated air horizontally to the interior of said furnace adjacent said second end wall at a point remote from said return port in said first end wall, the air in moving from said radiator channel to said air return port under influnce of said blower passing horizontally over the metal items to impart heat to the metal items, said additional heat radiator means being effective to supply radiant heat to such portions of said metal items in relatively close proximity thereto, said blower recirculating the air horizontally in the furnace to effect homogeneous heating of the metal items from top to bottom from side to side and from end to end by horizontally recirculating heated air relative to the metal items to oppose and reduce gravitational and density influences toward Stratification. 

1. A heat treat furnace, comprising a floor, a ceiling wall, a first side wall, a second side wall, a front wall, a rear wall, first heat generating and radiating means situated within the interior of said furnace and in relatively close proximity to said first side wall so as to define a first air passage extending from and having a first inlet near said rear wall toward said front wall, said first air passage including an outlet nearer said front wall, second heat generating and radiating means situated within the interior of said furnace and in relatively close proximity to said second side wall so as to define a second air passage extending from and having a second inlet near said rear wall toward said front wall, said second air passage including an outlet nearer said front wall, third passage means formed through a wall of said furnace in communication with said first inlet, fourth passage means formed through a wall of said furnace in communication with said second inlet, fifth passage means formed through said rear wall, said third fourth and fifth passage means being adapted for connection to associated air blower means whereby said third and fourth passage means are effective for directing air supplied by the discharge side of said blower means to said first and second air passages respectively, and whereby said fifth passage means is effective to accept and direct the air flowing horizontally from said first and second outlets and subsequently passing toward the rear wall to the inlet side of said associated blower means, and additional heat generating and radiating means situated in relatively close proximity to said rear wall inwardly thereof, said additional heat generating and radiating means being situated generally between said first and second side walls.
 2. A heat treat furnace according to claim 1, wherein said first heat generating and radiating means comprises a generally vertically extending baffle wall spaced from said first side wall and generally parallel thereto, a plurality of heat generating sources situated generally between said baffle wall and said first side wall, and wherein said baffle wall is formed to have an irregular vertically extending surface.
 3. A heat treat furnace according to claim 1, wherein said first heat generating and radiating means comprises a generally vertically extending baffle wall spaced from said first side wall and generally parallel thereto, a first plurality of heat generating sources situated generally between said baffle wall and said first side wall, and wherein said baffle wall is of a convoluted configuration with the convolutions thereof extending generally vertically.
 4. A heat treat furnace according to claim 2, wherein said baffle wall has a top edge in close proximity to the ceiling of the interior of said furnace and generally fixedly reTained in said close proximity, and wherein said baffle wall has a bottom edge constrained against laterial movement but free to raise and lower in accordance with contraction and expansion thereof due to temperature changes in said baffle wall.
 5. A heat treat furnace according to claim 4, including abutment means carried by said floor for constraining said lateral movement of said baffle wall, said abutment means comprising first and second abutment portions situated near said bottom ends and disposed on opposite sides of said baffle wall.
 6. A heat treat furnace according to claim 4, including baffle wall supporting means, said baffle wall supporting means comprising a plurality of hanger assemblies for supporting said baffle wall from said ceiling wall, each of said hanger assemblies comprising a main body portion extending upwardly through said ceiling wall as to have an upper end projecting beyond the top of said ceiling wall, a lower hook-like portion carried by said main body portion for reception through an accommodating aperture formed in said baffle wall near the upper edge thereof, and adjustment means cooperating with said upper projecting end for varying the heights of said hook-like portion relative to said ceiling wall.
 7. A heat treat furnace according to claim 1, wherein said first heat generating and radiating means comprises a generally vertically extending first baffle wall spaced from said first side wall and generally parallel thereto, a first plurality of heat generating sources situated generally between said first baffle wall and said first side wall, wherein said second heat generating and radiating means comprises a generally vertically extending second baffle wall spaced from said second side wall and generally parallel thereto, a second plurality of heat generating sources situated generally between said second baffle wall and said second side wall, and wherein each of said baffle walls has its top and bottom edges in at least close proximity respectively to said ceiling wall and a floor of the interior of said furnace.
 8. A heat treat furnace according to claim 7, wherein each of said baffle walls is hangingly supported from said ceiling wall, and wherein each of said baffle walls terminates short of said front wall in order to thereby define said first and second outlets as having a height substantially equal to the vertical distance from said floor to said ceiling.
 9. A heat treat furnace according to claim 7, wherein said first and second plurality of heat generating sources each comprise a plurality of generally U-shaped burner tubes extending vertically between respective ones of said baffle walls and related side walls.
 10. A heat treat furnace according to claim 7, wherein said floor comprises a lower outer metal wall, a plurality of platform like support surfaces extending generally from said front wall toward said rear wall, a first layer of mineral fiber insulation placed adjacent the inner surface of said lower outer metal wall, and a second layer of insulation placed adjacent the inner-most surface of said first layer of insulation, said second layer of insulation being of blanket-like configuration and composed or constituents high in percentages of alumina and silicon oxide.
 11. A heat treat furnace according to claim 7, wherein each of said side, rear, front and ceiling walls is comprised of an outer metal wall, a first layer of insulating material placed adjacent the inward surface of said outer metal wall, a second layer of insulating material placed adjacent the inward surface of said first layer of insulating material, and including retaining means for holding said layers of insulating material in position, said retaining means comprising a plurality of spaced hanger-like rods arranged as to be generally normal to and secured at respective one ends to said outer metal wall, said layers of insulating material being generally skewered onto said hanger-like rods and retained thereon by suitable removeable abutmenTs carried generally near the respective other ends of said hanger-like rods
 12. A heat treat furnace according to claim 11, wherein said first layer of insulating material comprises block form mineral fiber insulation;
 13. A heat treat furnace according to claim 1, wherein said fifth passage means comprises horizontally spaced first and second outlet conduit means, and wherein additional heat generating and radiating means is situated generally between said first and second outlet conduit means.
 14. A heat treat furnace according to claim 13, wherein said additional heat generating and radiating means comprises a generally vertically extending U-shaped burner tube.
 15. A furnace for heat treating such as annealing, normalizing, and stress-relieving metal items; said furnace having a structure and operation comprising a floor for supporting metal items to be treated, first and second side walls, first and second end walls rising from said floor, a ceiling wall on said side walls and end walls, and a door in one said wall for placing and removing metal items in said furnace, a baffle wall lying parallel to and relatively closely spaced from said first side wall, said baffle wall leading from said first end wall and terminating short of said second end wall, said baffle wall and said first side wall creating a radiator channel having an open end spaced from said second end wall, heat radiators between said first side wall and said baffle wall in said radiator channel, a blower having a suction side and an exhaust side at said first end wall, an air return port in said first end wall leading from the furnace interior to said blower suction side, an air delivery port in said first end wall leading from said blower exhaust side to said radiator channel between said baffle wall and said first side wall, and additional heat radiator means situated in relatively close proximity to said first end wall and said air return port, said blower thereby drawing air horizontally from the interior of said furnace walls and delivering the air horizontally to said radiator channel to pass the air horizontally over said radiators in said channel to heat the air, said radiator channel emitting the heated air horizontally to the interior of said furnace adjacent said second end wall at a point remote from said return port in said first end wall, the air in moving from said radiator channel to said air return port under influnce of said blower passing horizontally over the metal items to impart heat to the metal items, said additional heat radiator means being effective to supply radiant heat to such portions of said metal items in relatively close proximity thereto, said blower recirculating the air horizontally in the furnace to effect homogeneous heating of the metal items from top to bottom from side to side and from end to end by horizontally recirculating heated air relative to the metal items to oppose and reduce gravitational and density influences toward stratification. 